Treatment of sal-ammoniac skimmings.



G. RIGG.

TREATMENT 0F SAL AMMONIAG sKIMMINes.

APPLICATION FILED N0.V.12,v1910. 1,002,317, Patented Sept. 5, 1911.

2 SHEETS-SHEET 1.

fX/WITNESSESZ l /N tm t# f/L G. 11111111 TREATMENT 0F SAL AMMONIAG SKIMMINGS.

APPLIOATION FILED NOV.12, 1910.

1,002,317. patented sep1.5,1911.

2 SHEBTS-SHEET 2.

WITNESSES: INVENTOR ATTORNEYJ UNITED sTATEs PATENT oEEIcE.

GILBERT RIGG, OF PALMERTON,I'PENNSYLVANIA.

Y TREATMENT 0F SAL-AMMONIAC'SKIMMINGSS.

Specification of Letters Patent.

Patented Sept. 5, 1911.

Application filed November 12,/ 1910. Serial No. 592,001.

To all whom 'it may concern:

Be it known that I, GILBERT RIGG, a subject of the King of Gieat Britain, having a residence and ost-oiice 4address at Palmerton, county of) Carbon,. State of Pennsylvania, have invented certain new and useful Improvements in the Treatment of SalsAmmoniac Skimmings; and Ido hereby declare,

the following to be a full, clear, and exact description of the invention, such as will en able others skilled in the art to which it appertains to make and use the same.

My invention relates to certain new and useful improvements in the treatment of sal ammoniac skimmin'gs for the recovery of the chlorids of zinc and ammonium contained l therein, and for the. production of a residuum adapted for use as a spelter material, or`

as amaterial for the production of zinc compounds.

The leading) or characteristic feature ofy my invention consists in recovering the zinc chlorid in a liquid state and in a condition practically free from ammonium chlorid, the liquid zinc chlorid separating out, in itsv substantial entirety, from the vapors of ammonium chlorid, in the condensing receptacle. The process is preferably a continuous one, in the sense that the vapors of Zincchlorid and of ammonium chlorid are distilled over from a heated retort containing' have escaped liquefaction) are conveyed 0E continuously to a suitable absorber, or the like.

rlFhe practically quantitative recovery of the Zinc chlorid in the liquid form is due to the circumstance that the mixed vapors of zinc chlorid and ammonium chlorid enter the condenser in a transparent state, because of the conditions under which they are produced, which exclude damp vair and prod- "ucts of combustion from admixture with them, and to the further circumstance that the vapors are not suddenly chilled when they enter the condenser.A I haveA discovered that the presence of damp air, or of products of combustion, or the sudden chilling of the mixed vapors, occasion the formation of a tenuous fume clouding the' otherwlse transparent vapors and exceedingly difficult to condense. I believe that .I am the rst to have recognized the prejudicial influence of the factors referred to, and the first to have devised a process obviating and avoiding them. In the accompanying-drawings, Figure l represents a longitudinal central section, partly in elevation, of apparatus suitable for thevpractice. of the invention; Figs. 2 and 3 represent, on a somewhat larger scale, sections on the lines 2 2 and 3*?) respectively.

Similar letters of reference indicate simil lar parts throughoutthe several views.

Referring to the drawings, A indicates a heating furnace, having a Suitable perforated grate, indicated at a, upon which is charged the fuel, consisting preferably of ya mixture of three parts hard coal to one part` soft coal, the combustion being urged in any convenient manner, as, for instance, by a stean blower giving a regulable forced dra t.

B indicates a fire-'clay retort which may` conveniently be 1Q feet long, 2 feet 4 inches wide and 1 foot 4 inches high. This retort is set inthe furnace, as shown, so that the furnace gases may take their way through the passages indicated, which are designed to so distribute the heat as to keep it substantially uniform from end to end of the retort. The rear end of the retort, after the insertion of the skimmings charge is ladapted to be closed by tiles b luted in wit-h loam, so as to be air-tight. At thefront end of the retort is located the condenser C, which v may conveniently be a fire-clay tube partially closed at one end. Its open end is built into the retort B, and, at its Vforward end, it is provided with an aperture c to permit the condensed zinc chlorid to flow out. The condenser extends over the top of the fire box al which is covered with tiles e. A'

bric/k hood f is built around `the condenser, andis provided with a port which can be wholly or partially openedy or closed as de"- sired, as, for instance, through the instrumentality of a brick i. A suitable opening or openings, as, for instance, the openingj allows tire gases to enter the hood and may ioo ' will.

itself be wholly or partially opened or closed yas desired. This arrangement enables the temperature of the condenser to be varied at The furnace is provided with a stack D for the products of combustion said stack having a regulating slide valve la or thedike,

i, and a metal hood E and pipe m deliver likethe base of.an absorbing tower F, having a filling of checker work 1', as, for instance, fire brick. The tower is connected by a draft-pipe s with the stack D, yand is su plied wlth water from thewell G, by t e centrifugal pump II, and the pipes tshown,

. and a return pipe lv leads back to the well.

It will, of course, be understood that this Wash tower is but illustrative of one of a number of equivalent devices which might be'employed for the recovery of the ammonium salt. In the wash tower, the same Water is circulated from the well and returned thereto until sufliciently saturated with the ammonium salt to be worth concentrating. A pipe w having a suitable cut- 'offvalve fw is provided, to carry off the steam and ammonia which come olf during the early stages of the operation and which would otherwise tend kto chill the condenser.

The mode of operation of the invention may be briefly described as' follows: The sal ammoniac skimmings consisting, as usual, of zinc oXid, metallic zinc, zinc chlorid, ammonium chlorid, and foreign matter, such as fuel, fuel ash, etc., is charged into the retort B, and theretort is then carefully closed and luted at its rear end. Be- Vfore charging the skimmings into the retort they may be mixed with, coke breeze, of say asize that will', in screening pass through a screen of one-half inch mesh. With certain kinds of very fusible skimmings, this admixture tends to prevent the formation of a tough cake which would part with its chlorids more slowly: With such skimmings, the time required for the furnace operation is materially shortened by this expedient and the operation as a whole is correspondingly facilitated.

Under the influence of the heat of the products of combustion from the lire box, ythe volatile matters of the retort charge are driven off in stages.. The charge melts down in the furnace and avthe "fwater is driven off as steam.Y YShortly after the evolution of steam has begun, free ammonia makes its appearance and continues until thesteam has been expelled, these prelimi.

nary products being carried off by means of the pipe fw.' During this periodthe cutoffvalve w in the pipe 'w is open and the cut-off valve z, in the pipe p is closed. Finally, after the water has been driven off, the zinc chlorid is expelled, and also the remainder of the ammonia (as ammonium chlorid). At the beginning of this stage, the cut-off valve fw 1s closed and the cutoff valve h is opened. The condenser, in the meantime, has been brou ht to the desired temperature by admitting a regulable amount of the fire gases into the space be tween the condenser and the outlying brick hood. Upon the proper` regulation of the temperature `condltions prevailing in the condenser, -the efficiency of the process depends, and,y to this end, the n temperature of the condenser is maintained above that of the melting point of zinc chlorid (200 C.) and below its boiling point (730o (l), but nearer to the boiling oint than to the melting point thereof an preferably, at say from 500 C. to 600 C. In general the temperature of the condenser is adjusted so that the zinc chlorid flows out at a dullred heat. Under these circumstances, the zinc chlorid condenses to the liquid form with remarkable ease and issues from the condenser in a molten stream, through the tap aperture provided for the purpose. vThe temperature in the condenser is higher than the condensing temperature of the ammolnium chlorid vapors, and the condenser therefore act-s as a separator of the zinc chlorid from the ammonium chlorid vapors, which latter (together with any minor portion of uncondensed zinc chlorid) pass on into the wash tower or its equivalent, where they are recovered by absorption. When the absorption has reached fthe required' stage, the well water may be concentrated, in any suitable manner, for the recovery of salammoniac. When the ammonium chlorid vapors are accompanied with a portion of uncondensed zinc chlorid vapors, there is also recoverable from the well water 'a corresponding quantity of 'galvanizers crystals (2NH4C1 ;ZnC`l2) As hereinbefore indicated, the ammonium chlorid vapors, instead of being passed through a wash tower, may be re- 1 covered by passing them into a series of condensing chambers, under temperature conditions which will deposit them therein, thereby avoiding absorption and subsequent concentration; but, in general, the wash tower is found an efficient agent for their recovery and is readily managed and operated.

In the early stages of the operation, the watery vapor having been driven off from lthe charge, the vapors of zinc chlorid and ammonium chlorid pass into the condenser, free of moisture and out of contact either with damp air or with products of combustion.- In view of this circumstance and also in. After the zinc chlorid and ammonium chlorid have been worked oli' from the charge, the residue in the retort B forms a Zinkiferous material, containing'zinc oxid, at times some metallic zinc and the xed impurities originally present in the sal ammoniac skimmings, but substantially free from chlorin and ammonia. This residue is suitable either for the production of spelter, or for the production of zinc compounds as, for instance, oXid of zinc, or zinc salts.

Having thus described my invention, whaty I claim is:

l. The method of treating sal ammoniac skimmings for the recovery of the chlorids and the production of a residue suitable for thel making of spelter, which consists in heating the skimmings to a temperature above the boiling point of.v zinc chlorid, thereby volatilizing the zinc chlorid and ammonium chlorid and condensing the zinc chlorid to liquid form while avoiding the presence of a diflicultly-condensable fume in the condenser by preventing sudden chilling of the vapors and keeping them'out of contact with damp air and products of combustion; substantially as described.

2. The method of treating sal ammoniac skimmings, which vconsists in heatingv them to a temperature above the boiling point of zinc chlorid, thereby volatilizing the zinc chlorid and the ammonium chlorid, receiving the volatilized chlorids ina suitable condensing space and maintaining therein a temperature above the melting point of zinc chlorid and below its boiling point, whereby the zinc chlorid' is recovered in the liquid state; substantially as described.

3. The method of treating sal ammoniac skimmings, which consists in heating them to a temperature above the boiling point of zinc chlorid, thereby volatilizing, the zinc chlorid and the ammonium chlorid, receiving the volatilized chlorids in a suitable condensing space and maintaining therein a temperature above the melting point of zinc chlorid .and below its boiling point, but nearer to the boiling oint than to the melting point; substantial y as described.

4. The method of treating sal ammoniac skimmings, which consists in heating them to a temperature above 'the boiling oint 'of zinc chlorid, thereby volatilizing t e zinc chlorid and ammonium chlorid, receiving the volatilized chlorids in a suitable condensing space and maintaining therein a.

temperature above thel melting point of zinc chlorid and below its boiling point, and above the condensing point of the ammonium chlorid; substantially as described.

5. The method of treating sal ammoniac skimmings, which consists in heating them to a temperature above the boilingl point of zinc chlorid, thereby volatilizing the zinc chlorid and ammonium chlorid, receiving the volatilized chlorids in a suitable condensing space and maintaining therein a temperature above the melting point of zinc chlorid and below its boiling point, and above the condensing point of the ammonium chlorid and inally recovering the ammonium chlorid fumes by absorptlon; substantially 'as described.

6. The method` of treating sal ammoniac skimmings, which consists in heating them to a temperature above the boiling point of zinc chlorid, thereby volatilizing the zinc chlorid and the ammonium chlorid, receiving Ythe volatilized chlorids continuously in a suitable condensing space, maintaining therein a temperature above the melting point of zinc chlorid and below its boiling point and above the condensing point of ammonium chlorid, continuously drawing ofil the liquefied zinc chlorid and continu ously drawing ofi"Y the ammonium chlorid va ors; substantially as described.

The method of treating sal ammoniac skimmings, which consists in admixing with the sal ammoniacskimmings a quantity of solid fuel adapted to keep the charge ,open while it is disengaging its chlorids, heating the'skimmings to a temperature above the boiling point of zinc chlorid, thereby volatilizing the zinc chlorid and ammonium chlorid and condensing the zinc chlorid to liquid form while avoiding the presence of a diiicultly-condensable fume in the condenser by preventing sudden chilling of the vapors and vkeeping themlout of contact with damp air and products of combustion.

In testimony whereof I ax my signature, in presence of two witnesses.

GILBERT RIGG.

Witnesses:

E. Gr. TACY, JOHN GPENNIE. 

